1381 results about "Wave detection" patented technology

To calculate information on a relative distance or positional relationship between an interface section and an object by detecting an electromagnetic wave transmitted through the interface section, and using the electromagnetic wave from the object to detect a relative position of the object with respective to the interface section. Information on the relative spatial position of an object 101 with respect to an interface section 102 that has an arbitrary shape and deals with transmission of information or signal from one side to the other side of the interface section 102 is detected with a spatial position detection method. An electromagnetic wave 106 radiated from the object 101 and transmitted through the interface section 102 is detected by an electromagnetic wave detection section 103, and based on the detection result, information on spatial position coordinates of the object 101 is calculated by a position calculation section 104.

The invention relates to the technical field of terahertz spectrums, in particular to a graphene-based all-optically controlled ultra-high speed terahertz intensity modulator. The technical problems of low modulation speed and narrow spectrum range of the conventional terahertz intensity modulator are solved, and the application range of a system is widened. According to the graphene-based all-optically controlled ultra-high speed terahertz intensity modulator, gold nanoparticles are adopted, so that the photon absorption efficiency of graphene is enhanced, the concentration of photon-generated carriers is improved, the absorption of terahertz waves is further enhanced, and the modulation effect of the modulator is enhanced. The graphene-based all-optically controlled ultra-high speed terahertz intensity modulator comprises a terahertz wave generation device, a pumping light wave generation device, a terahertz intensity modulator and a terahertz wave detection device, which are connected to finish the design of the graphene-based all-optically controlled ultra-high speed terahertz intensity modulator. The graphene-based all-optically controlled ultra-high speed terahertz intensity modulator is mainly applied to the fields of terahertz communication systems and terahertz researches.

The invention discloses a harmonic wave detection method based on Fourier transformation, comprising the following steps: (1) carrying out oversampling and analog-to-digital conversion on a measured signal, and ensuring that data of two signal periods can be sampled from each group of data according to the maximum periodic value estimated by the measured signal; (2) filtering harmonic wave components outside fundamental waves by a digital low pass filter; (3) calculating a fundamental wave period by a periodic method; (4) extracting 2*N numbered data points within one period, wherein, N-1 is the highest harmonic order number; and (5) calculating the parameter of each harmonic wave component by utilizing a synchronous sample FFT. The method of the invention belongs to the signal processingtechnical field, and also can be used for spectrum analysis of other signals. Very high harmonic wave detection accuracy can be obtained by the method; the instantaneity can be doubled compared with three to five signal periods of a quasi-synchronizing method; and the time of two signal periods are only needed, and the fundamental wave frequency also can be accurately measured.

The invention discloses a fundamental wave based on Kaiser Window bispectrum line interpolation FFT (Fast Fourier Transform) and a harmonic wave detection method. The method comprises the following steps: analog-to-digital conversion and low-pass filtration treatment is conducted on the signal to be detected; the Kaiser Window with free proportion selection between the attenuation of a main lobe and side lobes, flexible design realization, low side lobe level and quick attenuation speed is adopted to conduct windowing FFT operation on the signal; and bispectrum line interpolation algorithm is used for detecting base wave and harmonic quantities of the detected signal. The following aspects are included: (1) analog-to-digital conversion and low-pass filtration; (2) the FFT operation based on the Kaiser Window; (3) base wave and harmonic wave parameters derived by bispectrum line interpolation and polynomial fitting.

Disclosed is radar wave detection and DFS (dynamic frequency selection) with high efficiency while considering, for instance, the power consumption of each communication station within an autonomous distributed network. At least one communication station runs in an interference avoidance operation mode, operates a radar wave detection section, and fulfills the obligation to issue instructions for radar wave detection and DFS for an approximately predetermined period of time. After the lapse of the approximately predetermined period of time, another communication station switches to the interference avoidance operation mode and assumes the obligation to issue instructions for radar wave detection and DFS. In other words, two or more communication stations sequentially run in the interference avoidance operation mode in a time sharing manner. Therefore, the average power consumption of the communication stations decreases.

In an image projection on a screen, an image projection apparatus improves the safety of entry into a projection region by the human body and does not bring about the increase of complexity of the configuration thereof owing to the improvement of the safety. A monitoring area is regulated on the outside of the projection area (3) of the screen (2). A detection wave such as infrared rays is emitted from a detection wave source (1c) of the image projection apparatus (1). A reflection wave from the monitoring area is detected by reflection wave detection means (1d) such as a CCD sensor. Whether the human body or an obstacle enters the monitoring space, which is surrounded by a detection wave (4) between the main body unit of the image projection apparatus (1) and the screen (2), or not is detected. Once the entry is detected, the intensity of the radiation light traveling toward the projection area (3) is reduced or cut off according to the situation or the degree of the entry.

The invention discloses a frequency self-adaptive real-time fractional harmonic wave detection method. Phase locking is conducted on power grid voltages through a phase locked loop, the power grid voltage frequency fg is obtained, the system control frequency fs is adjusted according to the power grid voltage frequency fg, when the power grid voltage frequency fluctuates, the number of sampling points of a system within the power grid fundamental wave period is kept unchangeable, the function of frequency self-adaptation of an n-harmonic-wave band-pass filter is achieved, and then subtraction is carried out on the input quantity of the n-harmonic-wave band-pass filter to remove mutual interference among all times of harmonic waves. Finally, n harmonic waves of a detected signal are extracted through the n-harmonic-wave band-pass filter, and then the harmonic waves of the detected signal can be accurately detected in a real-time and fractional mode.

The invention discloses a method and a device for selecting the small unit average constant false alarm rate for the real-time detection of a moving target of a synthetic aperture radar (SAR); the device comprises: a linear wave detector, a first reference unit, a first protection unit, a second protection unit, a detection unit, a comparator unit, a first average processing unit, a second average processing unit, a small-selecting comparator unit and a multiplier unit; the method comprises that: the image data of the synthetic aperture radar is carried out the linear wave detection and then is sequentially input into the detection unit; the both ends of the detection unit are respectively provided with one protection unit and the reference unit, the small value of the two values after averaging each reference unit is taken, and the threshold is obtained by multiplying the small value with the detection threshold; the detection unit and the threshold are compared to obtain the detection result; then, the image edge is carried out the detection to obtain the whole frame of the detected target image. The method solves the problems such as lower detection probability, high false alarm rate and vulnerability of the interference of the prior art; and the invention provides the system which has small calculation amount, simple operation, improved detection effect and is applicable to the real-time detection of the moving target.